Cathode sputtering apparatus for producing plural coatings in a confined high frequency generated discharge



Jan. 7, 1969 w. .1. CARLSON 3,420,767

CATHODE SPUTTERING APPARATUS FOR PRODUCING PLURAL COATINGS IN A CONFINEDHIGH FREQUENCY GENERATED DISCHARGE v Filed March 3, 1966 Sheet 1/ of 2INVENTOR T Mil/6 [fizz so/v ATTORNEYS Jan. 7, 1969 w. J. CARLSON3,420,767

CATH'ODE SPUTTERING APPARATUS FOR PRODUCING PLURAL COATINGS IN ACONFINED HIGH FREQUENCY GENERATED DISCHARGE Filed March 3, 1966 Sheet 2of 2 INVENTOR 5544/5 J (22460 ATTORNEYS United States Patent 3,420,767CATHODE SPUTTERING APPARATUS; FOR PRO- DUCING PLURAL COATINGS IN A'CONFKNED HIGH FREQUENCY GENERATED DESCHARGE Willis .7. Carlson,Minneapolis, Minn., assignor to Control Data Corporation, M nneapolis,Minn, a corporation of Minnesota Filed Mar. 3, 1966, Ser. No. 531,548US. Cl. 204298 Int. Cl. C23c 15/00 This invention relates to apparatusfor producing a plasma in a large container which is maintained at asubstantial vacuum and, in particular, this invention relates to meansfor producing a plasma in a portion onl of the large vacuum. Further,this invention relates to apparatus for producing on a plurality ofsubstrates, (for example, by sputtering) a layer of material on eachsubstrate.

In prior art apparatus for sputtering a film or layer of material on asubstrate, the number of substrates, upon which the layers can bedeposited or sputtered, is limited by the amount of mechanical fixtureswhich must be associated with the vacuum chamber.

In prior devices, a vacuum chamber containing an inert gas is providedin which the pressure is reduced to a low level so that the sputteringprocess may be employed. A target electrode is placed in the vacuumchamber together with the substrate upon which the target material isdeposited. A radio frequency coil is placed around the outside of thevacuum chamber so that when energized, the low pressure gas is convertedinto a plasma. A high voltage is placed on the target electrode and theions of the plasma are attracted thereto with such force that materialfrom the target plate is knocked loose therefrom and transferred to thesubstrate which is placed a small distance therefrom. A furtherelectrode is placed within the vacuum to provide a return path for thevoltage placed on the target electrode.

It is desirable that a large number of substrates have one or morelayers deposited thereon during one vacuum cycle and thereby take themanufacture of such products as magnetic thin films from a research typedeposit of one or two layers or films per chamber evacuation to aproduction machine where thirty-two (for example) films can be depositedin one evacuation. Typically, one deposit is possible every hour therebyproducing 256 films in an eight-hour day. This would reduce the cost ofproducing magnetic thin films to of a cent per bit. However, with theincrease in the number of substrates, the number of mechanical fixtureswhich must be provided also increases. This requirement conflicts withthe fact that the R-F coil is placed on the outside of the vacuumchamber.

Accordingly, it is an object of this invention to provide improvedapparatus for producing a plasma within a large vacuum chamber, wherethe plasma is restricted or confined to a definite portion of thevacuum, the R-F coil being placed inside the chamber.

Another limitation found in prior art devices is that only one layer canbe deposited on a substrate for a given vacuum cycle-that is, once thevacuum chamber is pumped down to a sufiiciently low presure, it ispossible to deposit only one layer on the substrate with prior artdevices. Before another layer can be deposited, it is necessary to breakthe vacuum to permit a new target of different composition to be enteredinto the chamber. Then the chamber is pumped down again and the secondlayer is deposited on the first layer. It is evident that the necessityfor creating and destroying the vacuum with each deposition is costlyand time consuming and not suitable to mass production.

6 Claims 3,420,767 Patented Jan. 7, 1969 Therefore, it is another objectof this invention to provide improved apparatus for depositing aplurality of layers of material on a substrate during a single vacuumcycle.

It is a further object of this invention to provide improved apparatusfor producing a plasma within a restricted portion of a large vacuum.

Other objects and advantages of this invention will become apparent tothose of ordinary skill in the art upon reading the appended claims andthe following detailed description of an illustrative embodiment of theinvention, in conjunction with the drawings, in which:

FIGURE 1 diagrammatically illustrates an embodiment of the inventionwhere a plasma is created Within a restricted portion of a vacuum;

FIGURE 2 is a side view of an illustrative embodiment of the invention;

FIGURE 3 is an end view of the embodiment shown in FIGURE 2;

FIGURE 4 is a partial cross-section taken along the line 44, shown inFIGURE 2;

FIGURE 5 illustrates a detailed portion of FIGURE 4; and

FIGURE 6 illustrates a further embodiment of the invention.

Referring to FIGURE 1, one of the basic concepts of "ice this inventionis illustratedthat is, the creation of a plasma within a restrictedportion of the space of the vacuum chamber 11. A substantially closedcoil or sheet ltl of electrically conducting material is placed withinthe vacuum chamber 11. Only the inert gas confined within the sheet 10will be ionized and made suitable for carrying out the sputteringprocess. Mechanical fixtures are diagrammatically indicated at block 13,these fixtures also being disposed within the vacuum to facilitate themass production multi-layer deposition process. These fixtures will bedescribed in detail hereinafter with respect to FIGURES 2 and 3.

Referring to FIGURE 2, there is also shown the cylindrical sheet 10 ofelectrically conducting material. As shown in FIGURE 4, there is a slit12 provided along the bottom of the sheet 16 across which high frequencyenergy, such as a radio frequency (R-F) voltage, may be applied.

Although the sheet is shown having a circular crosssection with respectto the axis of the cylindrical sheet, other cross-sections are alsopossiblesuch as, square and rectangular cross-sections as shown inFIGURE 6 where the sheet or coil 10 is nearly closed on four sides. Bythis method a plasma of sufficient density for sputtering can bedeveloped.

The connecting electrical cables to the opposite sides of the slit areshown in FIGURE 2 at 14 and 1-6. This electrical connection may bebalanced or unbalanced. Since sheet 10 is of solid construction and hasonly the slit 12 contained therein, the application of the R-F voltageto the sheet 10 will produce an R-F magnetic field within the sheetwhich will ionize the inert gas within the sheet 10, thereby creating aplasma substantially within a confined or restricted portion of thevacuum within the chamber 11, as shown in FIGURE 1. Thus, the plasma iscreated in a first space portion of the chamber 11 enclosed by the sheet10, whereas the mechanical fixtures 13, shown in FIGURE 1 and describedin more detail with respect to FIGURES 2 and 3, are disposed within asecond space portion of the vacuum chamber 11. The use of the sheet 10to create the plasma within a restricted portion of the vacuum allowsbetter coupling to the plasma, and a more oonfined plasma; therebyresulting in less cleanup of the system, less down time, and less laborcosts.

Plates 18 and 20 are disposed at the ends of the cylindrical sheet 10 inorder to restrict the plasma to the space within the sheet 10. Theplates 18 and 20' take the shape of circular disks, shown in FIGURE 3,with peripherally attached projections 22 and 24 provided so thattheplasma will be more effectively confined within the sheet 10. Thisresults from the fact that the inside diameter of the projections 22 and24- is slightly greater than the outside diameter of the sheet 10. Aslight gap, as indicated at 26 and 28, must be maintained between theplates 18 and 20 and the sheet 10* to insure the proper distribution ofelectricity on the sheet 10. The plates 18 and 20 are also normallygrounded electrically. Conventional support and grounding means forplates 18 and 20 have not been shown.

Insulated supports 36 and 32, as shown in FIGURE 2, are connected to thecylindrical sheet 10 and mounted at the base of the vacuum chamber 11.

Reference should now be made to FIGURE 4 which is a partialcross-section of the embodiment shown in FIGURE 2 taken along line 44.The sheet or coil 10 is also support for substrate holders 34, whichextend along the axial direction of the cylindrical sheet 18. Eachsubstrate holder typically contains four substrates 35. Only the ends ofsubstrates are shown in FIGURE 4. The holders are held in the sheet byplates 36 which extend along the axial direction of the cylindricalsheet 10 and by screws 38 attached through the sheet 10. Typically,eight of substrate holders 34 are disposed around the periphery of thesheet 10, as shown in FIGURE 4.

Reference should now be made to FIGURE which illustrates in detail oneway that the plates 36 may be employed to provide separation between,and sup-port for, the substrate holders 34. Other expedients will bereadily apparent to one having ordinary skill in this art.

Reference should now be made to FIGURES 2 and 3 which illustrate indetail the mechanical fixtures 13, shown in FIGURE 1. The basic purposeof the structure shown in FIGURES 2 and 3 is to provide the capabilityfor depositing on each of the plurality of substrates disposed along theinside of the sheet as shown in FIGURE 4, a plurality of layers or filmsof various materials during a single vacuum cycle. As already pointedout, the unique arrangement of a plurality of substrates disposed alongthe inside wall of a cylindrical sheet of electrically conductingmaterial which itself is disposed within a vacuum chamber as brought outin FIGURES 1 and 4, provides the mass production capability ofsubstrates having one layer of material deposited thereon. By combiningthe structure of FIGURE 4 with that shown in FIGURE 3, theabove-mentioned capability of depositing on each substrate a pluralityof layers of different materials during a single vacuum cycle isprovided. As also mentioned before, a truly efiicient mass productioncapability requires the ability to produce a plurality of layers on eachsubstrate for a single vacuum cycle in order to minimize waste of timeand money.

In FIGURE 3 there is shown a threaded rod 40 having a beveled gear 42mounted at the end thereof, which meshes with another beveled gear 44'mounted on a rod 46 which is connected to a point outside of the vacuumchamber (not shown). The rod 46 has a plurality of pinion gears 50, 52,5'4- and 56 threaded thereon. The pinion gears are arranged to mesh witha worm gear 58, which is mounted on a shaft 60, which is also connectedto a point outside of the vacuum chamber.

End plate 18 has a slit 62 therein which extends from the bottom of theplate to a point approximately at the center thereof. This slit isnormally covered by a rotatable cover 64. Lever 66, which is connectedto cover 64, causes the cover to be rotated to a position such as shownat 67, the lever 66 also being connected to a point at outside of thevacuum chamber. Lever 66 is diagrammatically shown and may be connectedto cover 64 by any of many well-known methods to cause the rotationthereof.

Respectively associated with each of the pinion gears are target membersor rods 70, 72, 74 and 76. Each target rod is made of a differentmaterial depending on the materials which are to be deposited on thesubstrates 35 for a given vacuum cycle. The rods 70 through 76 supplythe material which will be deposited on the substrates, the ions of theplasma attacking a given target and loosening therefrom the material tobe deposited. In order to attract the ions to the target, high voltageterminals 80, 82, 84 and 86 are respectively connected to the targets 70through 76 and the pinions 50-56. High voltage terminals 88 are alsoprovided at the center of plate 18.

The purpose of the mechanical structure shown in FIGURE 3 is to move adesired target rod into the space portion enclosed by the sheet 10, thetarget rod being eventually disposed substantially along the axis of thecylindrical sheet 10 and the electrical terminals associated with thetarget rod being in contact with the terminals 88 on the plate 18. Noelectrical wires to the terminals 88 are shown in the drawing. Parts 90,92 and 94 are supports for the mechanical structure.

Having now described the mechanical structure shown in FIGURE 3, adescription of its operation will now be given. The operation will bedescribed in relation to a multi-layer deposition process upon each of aplurality of substrates. Although a certain order of steps will be givenin describing the process, it should be clear that many of the stepscould be interchanged or their order completely reversed and the orderof steps chosen is for the purpose of illustration only.

The coil or sheet 10 is first removed from its mountings 31 and 33,shown on FIGURE 2, from the vacuum chamber. The substrate holders 34,together with the associated substrates 35, are lined along the insidesurface of the sheet 10, as shown in FIGURE 4, with the plates 36 beingpositioned on the sheet 16 to hold the substrate holders at theirappropriate places along the inside surface of the sheet 16.

The sheet 16 is next placed back in the vacuum chamber. The lever 66 isthen operated to remove the cover 64 from the slit or opening 62 in theplate 18 and to the position shown at 67. The rod 46 is next rotateduntil one of the targets 70 through 76 is positioned in front of theslit 62. When this one target is in front of the slit 62, the pinionassociated therewith will also be in mesh with the worm gear 58. The rod60 is next rotated to rotate the pinions associated with the desiredtarget. The rotation of the pinion causes the desired target rod to berotated through the slit 62 and into a position where it extends alongthe axis of the cylindrical sheet 10 while at the same time theelectrical terminals associated with the desired target will be inelectrical contact with the terminals 88 on the plate 18. Material fromthis one target will be deposited as the first layer upon all of thesubstrates 35 within the sheet 10.

The inert gas is introduced into the vacuum chamber, the pressure isreduced in the chamber, high voltage is applied to the terminals 88, anR-F voltage is applied to the wires 14 and 16, and the cover 64 isreturned to its normal position covering the slit 62 in the plate 18.Thus the sputtering process commences and the ions of the inert gasattack the target rod causing material to be loosened therefrom anddeposited on the substrates 35 which are all spaced a substantiallyequal distance from the rod aligned along the cylindrical sheet 10.

After the first layer has been deposited, the following steps take placein preparation for the deposition of the second layer without breakingthe vacuum produced in the chamber or without extinguishing the plasmaestablished in the cylindrical sheet 10. First, the high voltage isremoved from terminals 88, then the cover 64 is rotated to the position67, shown in FIGURE 3, by actuation of lever 66, which is connected to apoint outside the chamber, as stated before. The shaft 68 is nextrotated, from a point outside the vacuum, to remove the target rodinvolved in the first deposition. The shaft 46, which is also actuatedfrom a point outside the vacuum is next rotated to position one of thetarget rods 70-76 which will be used in the next deposition. When thedesired rod is positioned in front of the slit 62, the pinion associatedtherewith is in mesh with the worm gear 58; therefore, rotation of theshaft 60 from a point outside the vacuum chamber rotates the next targetrod into position along the axis of the cylindrical sheet in preparationfor the next deposition.

The cover 64 is returned to its normal position and the high voltage isreapplied to terminals '88 and the sputtering process recommences withthe material of the second target being deposited upon the layer firstdeposited upon the substrate.

Thus, there has now been described apparatus for producing a pluralityof layers or films on each of a plurality of substrates (in the example,32 substrates) during a single vacuum cycle. This is in accord with theobjects and advantages stated for the invention.

What is claimed is:

1. Apparatus for depositing on at least one substrate sputtered materialfrom a target electrode, comprising:

a container housing a chamber enclosing a space within said container,means to maintain an ionizable gas at sputterable pressures within saidcontainer;

means for moving said target electrode into and out of said chamber,means for applying energy at high frequencies to said chamber to ionizegas which is confined within the chamber whereby material is sputteredfrom said target when positioned within said chamber; and

means for positioning said substrate in the path of said sputteredmaterial.

2. Apparatus as in claim 1 wherein each substrate is disposed on theinside surface of said chamber.

3. Apparatus as in claim 1 wherein said chamber has a central axis, eachsubstrate being disposed on the inside surface of the chamber and thetarget electrode being positioned during sputtering along said centralaxis.

4. Apparatus as in claim 1 wherein said electrode moving means comprisesa device, housed within said container exterior to the chamber, having aplurality of target electrodes associated therewith and having means forselectively moving individual ones of the electrodes into and out ofsaid chamber.

5. Apparatus as in claim 1 wherein said chamber has a slit along oneside thereof, said energy applying means supplying energy across saidslit.

6. Apparatus as in claim 1 wherein said chamber is a sheet ofelectrically conducting material having a substantially central axis andopen ends, the chamber further including a pair of plates disposed atthe open ends of the sheet and spaced a small distance therefrom.

References Cited UNITED STATES PATENTS 2,146,025 2/ 1939 Penning 204-1923,250,694 5/ 1966' Maissel et al 204298 3,287,243 11/1966i Ligenza204l92 3,291,715 12/ 1966 Anderson 204-298 3,296,115 1/1967 Laegreid eta1 204298 ROBERT K. MIHALEK, Primary Examiner.

US. Cl. X.R. 204 192

1. APPARATUS FOR DEPOSITING ON AT LEAST ONE SUBSTRATE SPUTTERED MATERIAL FROM A TARGET ELECTRODE, COMPRISING: A CONTAINER HOUSING A CHAMBER ENCLOSING A SPACE WITHIN SAID CONTAINER, MEANS TO MAINTAIN AN IONIZABLE GAS AT SPUTTERABLE PRESSURES WITHIN SAID CONTAINER; MEANS FOR MOVING SAID TARGET ELECTRODE INTO AND OUT OF SAID CHAMBER, MEANS FOR APPLYING ENERGY AT HIGH FREQUENCIES TO SAID CHAMBER TO IONIZE GAS WHICH IS CONFINED WITHIN THE CHAMBER WHEREBY MATERIAL IS SPUTTERED FROM SAID TARGET WHEN POSITIONED WITHIN SAID CHAMBER; AND 